// SpinWait.cs
//
// Copyright (c) 2008 Jérémie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//
#define NET_4_0
#if NET_4_0
using System;

namespace System.Threading
{
    public struct SpinWait {
        // The number of step until SpinOnce yield on multicore machine
        const int step = 10;
        const int maxTime = 200;
        static readonly bool isSingleCpu = (Environment.ProcessorCount == 1);

        int ntime;

        public void SpinOnce() {
            ntime += 1;

            if (isSingleCpu) {
                // On a single-CPU system, spinning does no good
                Thread.Sleep(0);
            }
            else {
                if (ntime % step == 0)
                    Thread.Sleep(0);
                else
                    // Multi-CPU system might be hyper-threaded, let other thread run
                    Thread.SpinWait(Math.Min(ntime, maxTime) << 1);
            }
        }

        public static void SpinUntil(Func<bool> condition) {
            SpinWait sw = new SpinWait();
            while (!condition())
                sw.SpinOnce();
        }

        public static bool SpinUntil(Func<bool> condition, TimeSpan timeout) {
            return SpinUntil(condition, (int)timeout.TotalMilliseconds);
        }

        public static bool SpinUntil(Func<bool> condition, int millisecondsTimeout) {
            SpinWait sw = new SpinWait();
            Watch watch = Watch.StartNew();

            while (!condition()) {
                if (watch.ElapsedMilliseconds > millisecondsTimeout)
                    return false;
                sw.SpinOnce();
            }

            return true;
        }

        public void Reset() {
            ntime = 0;
        }

        public bool NextSpinWillYield {
            get {
                return isSingleCpu ? true : ntime % step == 0;
            }
        }

        public int Count {
            get {
                return ntime;
            }
        }
    }
    //public struct SpinWait
    //{
    //    // The number of step until SpinOnce yield on multicore machine
    //    const           int  step = 10;
    //    const           int  maxTime = 200;
    //    static readonly bool isSingleCpu = (Environment.ProcessorCount == 1);

    //    int ntime;

    //    public void SpinOnce ()
    //    {
    //        ntime += 1;

    //        if (isSingleCpu) {
    //            // On a single-CPU system, spinning does no good
    //            Thread.Yield ();
    //        } else {
    //            if (ntime % step == 0)
    //                Thread.Yield ();
    //            else
    //                // Multi-CPU system might be hyper-threaded, let other thread run
    //                Thread.SpinWait (Math.Min (ntime, maxTime) << 1);
    //        }
    //    }

    //    public static void SpinUntil (Func<bool> condition)
    //    {
    //        SpinWait sw = new SpinWait ();
    //        while (!condition ())
    //            sw.SpinOnce ();
    //    }

    //    public static bool SpinUntil (Func<bool> condition, TimeSpan timeout)
    //    {
    //        return SpinUntil (condition, (int)timeout.TotalMilliseconds);
    //    }

    //    public static bool SpinUntil (Func<bool> condition, int millisecondsTimeout)
    //    {
    //        SpinWait sw = new SpinWait ();
    //        Watch watch = Watch.StartNew ();

    //        while (!condition ()) {
    //            if (watch.ElapsedMilliseconds > millisecondsTimeout)
    //                return false;
    //            sw.SpinOnce ();
    //        }

    //        return true;
    //    }

    //    public void Reset ()
    //    {
    //        ntime = 0;
    //    }

    //    public bool NextSpinWillYield {
    //        get {
    //            return isSingleCpu ? true : ntime % step == 0;
    //        }
    //    }

    //    public int Count {
    //        get {
    //            return ntime;
    //        }
    //    }
    //}
}
#endif
